6 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
into many folds to provide a greater surface for the glands that secrete the shell 
of the cocoon (Fig. 11). These glands are spoken of by Iijima, but are not 
figured by him. 
Ina recent paper I (1896, p. 1048) have discussed the synonymy of Leidy’s 
Procotyla fluviatilis and expressed my belief in the identity of this species with 
Dendrocelum lacteum ; upon the evidence presented above, I wish to emphasize 
my conviction in this regard. The apparent differences between the forms are 
in the American form the possible greater prominence of the frontal adhesive 
organ, the more frequent variation in the number of the eyes, and the separation 
of the seminal duct from the glandular part of the male sexual organ. The 
first two of these differences, as I have endeavored to show, are differences in 
degree only, and have no systematic value. The discrepancy between my 
account of the male sexual organs and that of Iijima alone stands as a real 
difference. Although I can find no account of anything similar in other Tri- 
clads, there are conditions comparable to these in the male organs of Polyclads 
and Rhabdocels (Lang, 1884, and Graff, 1882), and it is possible that this 
detail has hitherto been overlooked in Triclads. 
Neither have I any hesitancy in placing under D. lacteum Girard’s D. pul- 
cherrimum and D. superbum. The former differs, he says (1851, p. 265), from. 
D. lacteum “by having three pairs of eyes instead of two,” while bis D. su- 
perbum (18519, p. 2) “gleicht vielleicht noch mehr als die vorgehende Art 
[D. pulcherrimum] den D. lacteum, wovon es sich unterscheidet durch kleinere 
dünnere Gestalt, zwei Paar Augen, vorstehendere Horner und rothe oder milch 
weiss Farbe.” It is significant, too, that Leidy (1852, p. 288) should have first 
ascribed his Procotyla fluviatilis to Girard’s D. superbum (see Woodworth, 1896", 
p. 1048), and that Girard, in his recent extended monograph of North American 
Turbellaria, makes no mention of these two old species of his. 
Planaria gonocephala Ducks. 
Figure 5. 
Planaria gonocephala Ducks, 1830, p. 83. 
Planaria gonocephaloides STIMPSON, 1857, p. 28. 
MAN, 1885, p. 69. 
Dugesia gonocephaloides Grrarp, 1851, p. 265; 1851°, p. 2; 1891, p. 188. 
Dissına, 1862, p. 498. Situr- 
Sides parallel, tapering gradually posteriorly to a rounded point. Anterior 
ar, the sides of the head making an angle of about 
end obtusely pointed, angul 
In alcoholic material the auricles are 
60°. Two angular cephalic appendages. 
not prominent, scarcely showing at all in some specimens. Length of head 
about 75 of the totai length of the animal. Eyes two, in a plane joining the 
apices of the auricles. Clear area surrounding the eyes sometimes elongated 
in the antero-posterior direction. Color, dark reddish brown to grayish brown, 
uniform. Posterior margins of auricular appendages free from pigment. 
Length 9 to 15mm., greatest breadth 4 to2 mm. (Two alcoholic specimens, 
which must have measured 20 mm. or more in length when alive.) 
